Medical balloons are increasingly used in a wide variety of medical procedures. Typically, an uninflated medical balloon is inserted into a body-space, e.g., blood vessel, urological vessel, etc. by means of a catheter. After positioning at the desired location within the body, the medical balloon may be inflated by introducing a pressurized fluid into the balloon through the catheter. The pressurized fluid causes the medical balloon to expand, and the adjacent body-space is similarly expanded. The fluid may then be withdrawn from the balloon, causing it to collapse to facilitate its removal from the body. Medical balloons are also used for temporarily occluding vessels, placing medical devices such as stents, drug delivery and heat transfer.
Medical dilation balloons may be used to perform peripheral, for example, below-the knee, angioplasty to open a stenosis or occlusion of an artery, with or without stent placement. In some instances, this procedure requires that the balloon be threaded through small blood vessels along a tortuous path. Placement of the balloon may require that the balloon be forced through long calcified occlusions. Consequently, a number of characteristics are desired for medical dilation balloons used in these procedures.
In order to traverse a tortuous path to and/or through an occlusion, a high degree of trackability is desirable. In this context, the term “trackability” refers to the capability to traverse sharp turns or branches of the vessels or body cavities through which a balloon must pass. Balloons having more flexible walls generally provide better trackability. Since the balloon may be pushed through narrow and/or occluded blood vessels, a low profile (i.e., diameter) in the deflated state is also desirable. Further, a balloon should have good scratch resistance to avoid damage if it is pushed through a calcified occlusion.
Balloons used to place stents (an expandable metal sleeve), should have high puncture resistance, particularly at the areas of the balloon at the end of the stent. To avoid damaging the blood vessel's walls, the dilation balloon should exhibit low compliance. Balloon compliance is a term used to describe the change in a balloon's diameter as a function of pressure. Since the balloon may be used to open or expand tough tissues such as strictures, scarred or calcified areas, high pressures may be required. Thus, a balloon used in these applications should have high operating and burst pressures. The rated burst pressure is typically the maximum pressure at which there is a statistical 95% confidence level that 99.9% of the population of balloons will not burst. High-pressure non-compliant balloons may have rated burst pressures of up to 20 atmospheres or higher.
Generally, high pressure, non-compliant balloons are formed from relatively noncompliant (e.g. relatively inelastic) materials such as oriented highly crystalline polyethylene terephthalate (PET) films. Such PET films provide high tensile strength, and may be used to form balloons with thin walls having high burst pressures. However, balloons formed from PET and similar materials having a high strength relative to wall thickness tend to be susceptible to puncture and scratching.
Non-compliant medical balloons for performing angioplasty and other medical procedures are known. U.S. Pat. No. 6,746,425 to Beckham discloses a semi-compliant medical balloon and methods for manufacturing the balloon. U.S. Patent Application Publication No. US 2006/0085022 to Hayes et al. discloses a semi-compliant medical balloon having an integral woven fabric layer and methods for manufacturing the balloon. U.S. Patent Application Publication No. US 2006/0085023 to Davies, Jr. et al. discloses a medical balloon having strengthening rods and methods for manufacturing the balloon. U.S. Patent Application Publication No. US 2006/0085024 to Pepper et al. discloses a semi-compliant medical balloon having an integral non-woven fabric layer and methods for manufacturing the balloon. U.S. Pat. No. 6,746,425 and Publication Nos. US 2006/0085022, US 2006/0085023 and US 2006/0085024 are hereby incorporated herein by reference.
However, a need exists for improved medical dilation balloons having a low degree of compliance, thin walls, puncture resistance and improved trackability.